Future variability of droughts in three Mediterranean catchments

Abstract

In the present study, we analyze the magnitude and frequency of long-term droughts throughout the present century in Catalonia in the north-eastern Iberian Peninsula (Spain). In fact, this western Mediterranean region has recently suffered one of the most extreme dry episodes (2006–2008) in the last decades. This calls for further study of future perspectives of drought variability at the local scale. We selected three medium-sized catchments on the Catalan littoral: Fluvia, Tordera and Siurana. We employed both instrumental and simulated temperature and rainfall data to calculate two multi-scalar drought indices: the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Instrumental data consisted of several weather stations for a recent period: 1984–2008. Future projections covering the 2001–2100 period were extracted from a dynamical downscaling procedure at a 15-km horizontal grid resolution, nesting the mesoscale model MM5 into the atmosphere–ocean coupled model ECHAM5/MPI-OM, performed by the Meteorological Service of Catalonia. We calculated 24-month SPI and SPEI values for the instrumental and simulated periods, and no changes were found in drought variability for the early twenty-first century. For the mid-century, high climatic variability was detected, as extremely dry and wet periods might alternate according to the SPI values. At the end of the present century, we generally detected, particularly in the dry catchment of southern Catalonia, Siurana, more severe and longer droughts than the last extreme drought (2006–2008). There is a need to implement appropriate and specific adaptation strategies for water management of each catchment over the next decades to reduce the risk of the forecasted drought conditions.